This Phase II study is designed to evaluate the antitumor efficacy of crenolanib (CP-868,596) in patients with recurrent high grade glioma and in patients with low grade glioma. Concurrently, the pharmacokinetics, tumor penetration and ability of crenolanib (CP-868,596) to inhibit PDGFR signaling will be evaluated when given as neo-adjuvant therapy to patients with radiographic evidence of malignant glioma prior to initial surgery.